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System broke. No signal to monitor. Help!

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July 1, 2009 7:38:23 PM

I have a partially home-built small form factor PC system. It just stopped working suddenly. The screen froze. So I had to power down, then power back up the system.

The fan spins back up, the hard drive lites up, and everything ~sounds~ normal. But my LCD monitor remains blank! It does not detect a signal from my system. It's hooked up with DVI connection.

I hooked up my LCD to a laptop, and it works fine. So my LCD is not an issue.

My system also has a regular VGI connector, so I tried that too. No luck.

My system is screwed and I can't even go through my usual trouble shooting steps since I can't see jack. No P.O.S.T screen, no nothing. My LCD simply says "no signal detected".

Please help me trouble shoot this. What can cause the signal from the system to the monitor to suddenly not work? Could my CPU be fried? Or RAM? What components are suspect here?





a b B Homebuilt system
July 1, 2009 7:47:54 PM

Could be any number of things. Bad RAM or PSU would be my first guess. I'd go through the checklist in the "READ before posting about boot problems!" sticky to find the cause of your problem.
July 1, 2009 7:57:59 PM

Thanks. Will try the RAM sticks one by one trick. I haven't considered the PSU to be a possible problem, as the fan and hard drive seems to spin fine.
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a b B Homebuilt system
July 1, 2009 8:38:30 PM

A lot of times a dying PSU will still be able to spin things like fans and hard drives but not provide enough clean power to run the core components. The fact that the fans spin certainly doesn't mean the PSU is working correctly.
July 2, 2009 6:59:53 PM

So here's an update:

- Removed my tv tuner card, DVD drive, and one 1 stick of RAM = System boots back up. Yay!!!

- Put back the other stick of RAM = random results on several tries.
- Boots but freezes
- no boot (no signal to monitor)

- Take out same stick of RAM, but plug DVD drive back in = system functioning normal. Yay.

So it ~seems~ that I have a bad stick of RAM. However, this isn't conclusive, because I haven't tried to swap out the good stick with the supposedly bad stick yet.

But I am making progress! (And at least my system works, even though my RAM is now halved)
a c 122 B Homebuilt system
July 2, 2009 9:42:36 PM

That's the basic approach. You can either pull components one at a time until the system starts working. Or you can pull everything except CPU and heatsink, then add parts until it stops working.

I favor the latter approach because I can quickly check the core components - motherboard, CPU, and PSU.
July 3, 2009 8:48:23 PM

So I went back in and did some comprehensive RAM testing (using Memtest 86), and jotted down the results. Here are the results. Note that I have 2 RAM slots, which I'll call Slot 1 and Slot 2, and I'll call my Ram sticks "ramA" (the one that's already in Slot 1 before I started these Memtests) and "ramB" (the allegedly bad one I took out at the end of my previous post).


Test 1: Removed both sticks, then put ramB in slot 1.
Results: No errors. Odd, so it seems the allegedly bad ram isn't bad after all.

Test 2: Remove, then put ramA in slot 1.
Results: No errors. OK, so both sticks seem to be good by themselves.

Test 3: Put ramA in slot1 and ramB in slot2.
Results: Memtest froze midway! Then when I force a reboot, there's no signal to LCD again!

Test4: Switch them up. ramB in slot1 and ramA in slot2
Results: LCD works again, boot to memtest ok, but froze at 62%. When I reboot after the freeze, again no signal monitor.

Notes so far: So it seems that both of sticks together is causing the problem, and very consistently! My next test will be to test to see if my DIMM slot2 itself is the culprit.

Test5: Remove both sticks. Put ramB in slot 2
Results: Memtest ran. Errors reported at around 20% of test! (ECC correctable error). And then it reboots itself then the test is about 60% done. But when it reboots, no signal to monitor again.

Test6: Remove stick. Put ramA in slot 2
Result: Memtest ran, then suddenly screen goes crazy with colors midway. need to reboot again.


In the end, I went back to working with one stick of ram (RamB in Slot1), and I'll run my system like this for a while to see if anything develops. But my system ~seems~ to work fine so far, but with 1/2 the RAM.

So all in all, it seems the DIMM slot 2 itself is the culprit! (ie mobo is bad). Is this a fair conclusion? Can anyone think of anything else?
!